This line of reasoning kept me away from password managers for a while, but I’ve been using Bitwarden for almost a year now, and I could never go back.

You’re technically right, but a better way to look at it is that it reduces your surface of attack from many weak points, down to one, very strong and secure point (assuming you use a reasonably strong password for your vault, and don’t log into your vault on public networks or anything like that).

But at the end of the day, using a password manager is vastly superior to relying on your memory, which is what many people still do.